Rubber connectors are typically utilized to provide a water-tight seal between an opening in a manhole assembly and a pipe extending into the opening U.S. Pat. No. 4,159,829 assigned to the assignee of the present invention discloses a conventional bidirectional connector formed from an extrusion having a hollow, pear-shaped head portion integrally joined to a T-shaped anchoring flange. The extrusion is cut to length and curled to form a substantially right cylinder configuration with the mating edges being joined. The pear-shaped portion deflects from a radially inward orientation upon insertion of a pipe. A single cavity extends through the head portion to provide the head portion with added resiliency and provides moderate sealing pressure. U.S. Pat. No. 4,508,355 assigned to the assignee of the present invention constitutes an improvement over U.S. Pat. No. 4,159,829 by providing a gasket of similar shape having a plurality of internal cavities extending longitudinally through the head portion to provide the desired resiliency while at the same time providing improved stability of gasket configuration which yields a stronger and more uniform seal around the exterior of the sewer pipe including portions of the surface which may be significantly out-of-round.
The above designs nevertheless have the disadvantages of providing a water-tight seal which weakens as the water pressure applied to the gasket increases and which has very narrow tolerance limits with regard to the range of pipe outer diameter which can be accepted by a gasket thereby greatly increasing the number of gaskets required to cover a large range of pipe outer diameters, typically from 4" to 84".